1. Technical Field
This invention relates to liquid level sensors, and more particularly to a capacitive liquid level sensor for sensing the level of a liquid within a reservoir, where the sensor is generally immune to changes in the dielectric constant of the fluid and the orientation of the sensor about the center of the plates.
2. Discussion
Liquid level sensors are used in a wide variety of applications to detect the levels of fluids within various forms of reservoirs. Frequently, such sensors are employed in the automotive industry to sense the level of oil in an oil pan or sump, or the level of transmission fluid, just to name a couple of applications.
In many applications, and particularly in applications where the reservoir or sump is located on a moving vehicle such as an automobile, tractor or earth moving equipment, the vehicle will be required to traverse uneven ground which will cause the liquid in one or more reservoirs of the vehicle to shift. For example, when the vehicle begins moving up an incline, the orientation of the upper level of oil in an oil reservoir of the vehicle may change significantly. This in turn may cause an oil level sensor disposed in the oil reservoir to erroneously indicate that the oil level has changed (for example, decreased) to an unacceptable degree. In other words, the change in orientation may cause the level sensor to provide inconsistent and erroneous indications as to the true level of the oil in the reservoir.
It would therefore be highly desirable to incorporate a liquid level sensing device which is capable of accurately indicating when the level of a liquid in a reservoir has reached a predetermined point regardless of changes in the orientation of the reservoir.
It would also be highly desirable to provide a liquid level sensor which is relatively inexpensive to construct, highly reliable, relatively compact and lightweight, and readily usable in a wide variety of liquid level sensing applications with little or no modifications.